Why A Duck? by Frank M. BlandThis Official Unofficial Marx Brothers Web Site has it all. The people, the movies, sounds, pictures etc.
(This is a copy of the site originally available under the domain "whyaduck.com")

Marxology by Mikael UhlinConcentrating on the earlier years of their career.

"A Night in Elsinore" by Richard Nathanthe author describes it as " 'Hamlet' as it would have been performed by Groucho Marx"

You bet your life by Arthur Marxarticle by Arthur Marx in the magazine 'Cigar Aficionado'

Find-A-Grave by Location by Jim TiptonInformation where the graves of famous people (including the Marx Brothers) can be found

Marxist Propaganda by Dave Papeincludes a bunch of sound files (AU format) and a couple of film clips. He's also included scans of several Marx Brothers movie posters. alternative address (hasn't been updated for a while)